Russia blasted a TV tower in Ukraine’s capital and rained missiles on Kharkiv on Tuesday, intensifying its assault of Ukrainian cities in a tactical move after its six-day invasion stagnated.

A US official claimed a miles-long armored column bearing down on Kyiv had made no gains in the last 24 hours, possibly due to logistical issues, a lack of gasoline and food, and a pause to rethink tactics.

Russia’s defense ministry has advised inhabitants of Kyiv to escape, threatening to hit unnamed places utilized by Ukraine’s security forces and communications.

Speaking in a heavily guarded government compound in Kyiv, Ukrainian President Volodymyr Zelenskiy said Russia must “first stop bombing people” before peace talks could make any headway.

In a joint interview with Reuters and CNN, Zelenskiy also urged NATO members to impose a no-fly zone to stop Russia’s airforce, something the military alliance has ruled out.

As Zelenskiy, unshaven and wearing simple khaki clothes, spoke, news came that a Russian missile had struck a TV tower near the Babyn Yar Holocaust memorial site in Kyiv, killing at least five people.

Zelenskiy, who also spoke by phone for 30 minutes with U.S. President Joe Biden on Tuesday, said the artillery barrages on the eastern city of Kharkiv amounted to “state terrorism”.

Biden and Zelenskiy discussed how Russia had intensified attacks on sites used by civilians, the White House said. The U.S. president is expected to highlight Western unity over Ukraine in his State of the Union address later on Tuesday.

‘SHAMBOLIC’

President Vladimir Putin has drawn global condemnation and sanctions that have already sent the rouble into freefall and forced Russians to queue outside banks for their savings.

The West has imposed heavy sanctions on Russia to shut off its economy from the global financial system, pushing international companies to halt sales, cut ties, and dump tens of billions of dollars’ worth of investments.

But nearly a week since Russian troops poured over the border, they have not captured a single major Ukrainian city after running into far fiercer resistance than they expected.

“Looking at the Russian operation so far, they’re having tremendous problems with logistics and communications. The whole effort seems shambolic,” Michael Kofman, an expert on the Russian military at Washington’s Wilson Center, wrote in a tweet.

Many Western military analysts fear that Russia will now fall back on tactics which call for crushing bombardment of built-up areas before trying to enter them.

A senior U.S. defence official, speaking on condition of anonymity, said:

“One reason why things appear to be stalled north of Kyiv is that the Russians themselves are regrouping and rethinking and trying to adjust to the challenges that they’ve had.”

The Russians have been surprised not only by the scale of Ukrainian resistance but also by poor morale among their own forces, some of whom surrendered without a fight, the official said, without providing evidence.

Russia still has more forces to throw into the fight, though.

Russia’s Defence Minister Sergei Shoigu said the “special military operation” would continue until it had achieved its goals, defined by Putin as disarming Ukraine and capturing the “neo-Nazis” he says are running the country.